Induction of mucosal healing in inflammatory bowel disease (IBD) is associated with reduced hospitalizations and surgeries. Healing of the mucosal barrier requires control of the destructive inflammatory response as well as restitution of the epithelial barrier through enhanced proliferation and generation of new crypt structures. Although it is clear that induction of Wnt/B-catenin activation is a key factor in intestinal stem ell (ISC) and progenitor cell (PC) activation, there are few researchers that examine the regulation of B-catenin activation in colitis where mucosal healing and inflammation-induced dysplasia are major clinical concerns. Studies performed during the prior award period demonstrated that Akt phosphorylation of B-catenin increases in ISCs during colitis and colitis-induced cancer. The present proposal makes use of a novel genetic model for reducing PI3K signaling in colonic intestinal epithelial cells (IEC) during colitis. Data already produced in VilCre/pik3r1fl/fl mice given DSS colitis suggest that PI3K-mediated B-catenin activation plays a major role in wound healing. Acute and chronic forms of DSS colitis will be generated in VilCre/pik3r1fl/fl mice for in vivo studies in AIM 1 to examine the role of IEC class 1A PI3K in mucosal healing, B-catenin activation and ISC/PC gene expression (using novel enteroid cultures). Studies in AIM 2 utilize bone marrow chimera (BMC) mice to examine TNF-induced IEC B-catenin signaling in radioresistant epithelial populations in DSS colitis mice. AIM 3 studies examine the role of Nox1 in B-catenin activation using B6->Nox1-/- BMC DSS colitis mice. Together the studies propose that TNF-induced NOX1 stimulates PI3K-mediated B-catenin activation and ISC/PC gene expression to determine crypt responses in IBD. The underlying hypothesis is that inflammation-induced B-catenin signaling enhances epithelial regeneration and induces chronic architectural distortion by increasing ISC and progenitor cell expansion during colitis. The clinical relevance of these studies is great given that we hope to identify novel approaches to IBD therapy and chemoprevention.